My favorite radio show with a discussion about how 3/4 of the food we eat globally comes from 12 species of plants and 5 animals. Why is this dangerous? Lack of genetic diversity is a problem, and it is hidden to most of us. Any one of these crops could be wiped out by one disease! 

This is without even considering the effect on our health of eating these foods that have been most convenient for giant agricultural business. These foods have been hybridized for shelf stability and easy shipping. Not for health and nutrition. Or even flavor. 

Eat widely! Get away from the main-stream foods, eat from your local farmers market and eat stuff that doesn't find it's way onto Safeway shelves!